Japanese Patent Application No. 2015-249302 by another application of the present applicant discloses a circuit configuration of FIG. 27. A semiconductor apparatus illustrated in FIG. 27 includes an inverter IVU and various control circuits for the inverter IVU. This inverter IVU includes high-side switches HSWu, HSWv, and HSWw of three phases (u-phase, v-phase, and w-phase) and low-side switches LSWu, LSWv, LSWw of three phases. To the inverter IVU, an input source voltage VIN is supplied using a reference source voltage GND as a reference. The inverter IVU supplies electricity to a load LD of the motor, by generating current AC voltages (floating voltages) VSu, VSv, and VSw of three phases to load drive terminals PN_OUTu, PN_OUTv, and PN_OUTw, by, for example, PWM (Pulse Width Modulation) control.
The various control circuits include high-side control circuits HCTu, HCTv, and HCTw controlling and protecting the high-side switches HSWu, HSWv, and HSWw of three phases and low-side control circuits LCTu, LCTv, LCTw controlling and protecting the low-side switches LSWu, LSWv, and LSWw of three phases. Further, the various control circuits include an MCU (Micro Control Unit), high-side temperature detection circuits TChu, TChv, and TChw of three phases, and low-side temperature detection circuits TClu, TClv, and TClw of three phases.
The temperature detection circuit TChu includes two diodes DD1a and DD1b, two current sources IS1a and IS1b, and a differential amplifier circuit AMP1. The cathode of the diode DD1a is coupled to the anode of a temperature detection diode TDhu, while the cathode of the diode DD1b is coupled to the cathode of a temperature detection diode TDhu. The cathode of the temperature detection diode TDhu is coupled also to the load drive terminal PN_OUTu (floating voltage VSu).
The current source IS1a is coupled between a source voltage VDD and the anode of the diode DD1a, and controls a current to flow in a forward direction through the temperature detection diode TDhu via the diode DD1a. The current source IS1b is coupled between the source voltage VDD and the anode of the diode DD1b, and controls a current to flow through the diode DD1b in a forward direction. The differential amplifier circuit AMP1 detects a differential voltage between the anode of the diode DD1a and the anode of the diode DD1b, and transmits a result of this detection to an analog/digital converter ADC1 of a controller CTLU. Though not illustrated, details of the temperature detection circuits TChv and TChw are the same as those of the temperature detection circuit TChu.
The temperature detection circuit TClu includes a current source IS2 and a differential amplifier circuit AMP2. The current source IS2 is coupled between the source voltage VDD and the anode of the temperature detection diode TDlu, and controls a current to flow in a forward direction through the temperature detection diode TDlu. The cathode of the temperature detection diode TDlu is coupled to a reference source terminal PN_GND (a reference source voltage GND). The differential amplifier circuit AMP2 detects a differential voltage between the anode and the cathode of the temperature detection diode TDlu, and transmits a result of this detection to an analog/digital converter ADC2 of the controller CTLU. Though not illustrated, details of the temperature detection circuits TClv and TClw are the same as those of the temperature detection circuit TClu.
FIG. 28 illustrates an example of an operation of the semiconductor apparatus illustrated in FIG. 27. The horizontal axis indicates the time elapsed, while the vertical axis indicates the voltage level or the high/low level. FIG. 28 illustrates an operation of u-phase, and the same applies to the v-phase and the w-phase.
In a time T1, a low-side switch signal LOu to be a gate input of a low-side transistor TRlu is at the “H” level, while a high-side switch signal HOu to be a gate input of a high-side transistor TRhu is at the “L” level. In the time T1, a current from the current source IS1a flows through the temperature detection diode TDhu via the forward bias diode DD1a, while a current from the current source IS1b flows through the forward bias diode DD1b. 
At this time, at the temperature detection diode TDhu, a forward direction voltage depending on the temperature (specifically, having the negative temperature characteristic) is generated. At the anode of the temperature detection diode TDhu, a temperature voltage signal TOHu corresponding to the forward direction voltage is generated, using the floating voltage VSu as a reference. The values of the currents from the current sources IS1a and IS1b are the same, and, though not limited, are smaller than 1 mA, for example. In the low-side time, the differential amplifier circuit AMP1 detects a forward direction voltage of the temperature detection diode TDhu through the diodes DD1a and DD1b. The same applies to the case in times T3, T5, and T7.
In a time T2, the low-side switch signal LOu is at the “L” level, while the high-side switch signal HOu is at the “H” level. In the time T2, the diodes DD1a and DD1b become reverse bias. Thus, an output signal TIHu of the differential amplifier circuit AMP1 is at the “L” level. That is, the temperature detection diode TDhu does not perform temperature detection. The same applies to the case in times T4 and T6.
Japanese Unexamined Patent Application Publication No. 2011-133420 discloses a configuration in which the cathode of the high-side temperature detection diode is coupled to the ground.